The role of bacterial capsular polysaccharides and the pathways that produce them are integral in human health and disease playing a fundamental role in bacterial pathogenesis as well as essential symbiotic relationships with animals. A detailed understanding of the process and factors that regulate production of these macromolecules is of utmost importance to understanding how capsular polysaccharides affect healthy and diseased states. The focus of this proposal is on capsular polysaccharide A expressed on the cell surface of the symbiotic prokaryote Bacteroides Fragilis. This is an important target for detailed investigation since studies will provide tools and approaches for understanding the role of capsular polysaccharides in symbiotic microbes that may be used in enhancing human health. In addition, this pathway represents an uncharacterized biosynthetic system that is experimentally tractable and would offer insights and new methodological approaches for deriving information on the general biosynthesis of bacterial polysaccharides in pathogenic as well as symbiotic bacteria. The gene locus responsible for the biosynthesis of the tetrasaccharide repeat unit of capsular polysaccharide A has been identified. However, unambiguous biochemical analysis of the proteins produced from this gene locus has not been performed. Gene locus analysis has identified proteins homologous to four glycosyltransferases, a galactopyranose mutase, and a sugar aminotransferase, a protein responsible for pyruvation, a flippase and a polymerase. In this program we will use chemical and kinetic approaches to identify the biosynthetic route to capsular polysaccharide A, which can only be partially predicted by sequence analysis alone. In doing so, we will learn a great deal about nucleotide diphosphate sugar modifying enzymes and oligosaccharide glycosyltransferases that are currently poorly understood. PUBLIC HEALTH RELEVANCE: The role of bacterial capsular polysaccharides and the pathways that produce them are integral in human health and disease playing a fundamental role in bacterial pathogenesis as well as essential symbiotic relationships with animals. The focus of this proposal is on capsular polysaccharide A expressed on the cell surface of the symbiotic prokaryote Bacteroides Fragilis. In this program we will use chemical and kinetic approaches to elucidate the biosynthetic route to capsular polysaccharide A, enhancing the opportunity to utilize this biomolecule as a therapeutic for diseases ranging from Multiple Sclerosis to Inflammatory Bowel Disease.